This invention relates to a system and method for utilizing hydrocarbon liquids, or other liquids in which salt is insoluble, in underground cavities formed in salt deposits for producing electrical power.
So-called pumped energy storage systems are designed to, in effect, take surplus power from electrical power generating systems during low power demand or off-peak periods, store the power, and then recover it for use during peak power demand periods. This might be accomplished by hydro pumped storage systems consisting of a surface reservoir, an excavated underground reservoir, an underground powerhouse having an electrical power generating unit, and conduits for connecting the surface reservoir to the underground powerhouse and also for connecting the powerhouse to the underground reservoir. During heavy load periods, water from the surface reservoir is directed to the powerhouse to drive the power generating units, with the discharge being directed to the underground reservoir. During light load periods, water from the underground reservoir is pumped back to the surface reservoir to await a heavy load period when additional power will again be needed. Such a system is described in "An Assessment of Energy Storage System Suitable For Use By Electric Utilities", EPRI EM-264, Project 225, ERDA E (11-1)-2501, Final Report, Volume 3, July, 1976, prepared by Public Service Electric and Gas Company Research and Development Department, Newark, New Jersey 07101. Also see U.S. Pat. No. 3,643,426, issued Feb. 22, 1972.
Some of the drawbacks of pumped energy storage systems such as that described above are the unavailability of suitable sites for both above ground and underground reservoirs, the possible harmful environmental impact of providing above ground reservoirs for energy storage, and the high cost and difficulty of hard-rock mining or excavating the underground reservoir.
In the past, underground reservoirs have typically been utilized or at least suggested for utilization for storing petroleum products. Thus, U.S. Pat. No. 3,385,067 discloses storing petroleum in a pair of interconnected underground cavities formed in a salt bed. More recently, an article in Newsweek (Aug. 22, 1977 at page 55) described the government's strategic oil reserve program in which oil would be stored in cavities formed in salt domes. This is considered an attractive alternative to above ground storage of petroleum because of the greatly reduced costs of the underground storage. Of course, with such passive storage of petroleum, the petroleum is not utilized in any way until it is removed from storage for use as a fuel, lubricant, etc.